JPH0519354B2 - - Google Patents
Info
- Publication number
- JPH0519354B2 JPH0519354B2 JP57231807A JP23180782A JPH0519354B2 JP H0519354 B2 JPH0519354 B2 JP H0519354B2 JP 57231807 A JP57231807 A JP 57231807A JP 23180782 A JP23180782 A JP 23180782A JP H0519354 B2 JPH0519354 B2 JP H0519354B2
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- Prior art keywords
- image signal
- gradation
- density
- digital
- coordinate
- Prior art date
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- 238000006243 chemical reaction Methods 0.000 claims description 47
- 238000012937 correction Methods 0.000 claims description 42
- 238000012545 processing Methods 0.000 claims description 24
- 238000003672 processing method Methods 0.000 claims description 14
- 238000000034 method Methods 0.000 claims description 10
- 230000006870 function Effects 0.000 description 13
- 238000010586 diagram Methods 0.000 description 9
- 230000009466 transformation Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- 230000000007 visual effect Effects 0.000 description 2
- 238000006073 displacement reaction Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 238000003384 imaging method Methods 0.000 description 1
- 238000007430 reference method Methods 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 238000000844 transformation Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
- H04N1/40—Picture signal circuits
Landscapes
- Engineering & Computer Science (AREA)
- Multimedia (AREA)
- Signal Processing (AREA)
- Image Processing (AREA)
- Facsimile Image Signal Circuits (AREA)
Description
産業上の利用分野
本発明は、写真等の階調画像を光電走査によつ
て読み取つた画信号の階調補正を行なう画信号処
理方法に関するものである。
従来の構成とその問題点
写真等の階調原稿を光電走査して得られた読取
画信号を処理する装置、例えば画像スキヤナ装置
や撮像装置にあつては、読取画信号を画像読取素
子や画像記録または表示素子の特性に整合させる
目的、および画像の品質を人為的に加工する目的
で種々の画信号処理回路を具備している。特に近
年の画像処理装置にあつては階調特性を人為的に
変換する機能を持つものが多い。第1図に従来の
画信号処理装置における読取画信号処理の処理、
特に階調変換に係る処理の流れを示す。第1図の
従来例にあつては、原稿の画像濃度の指数に反比
例する読取画信号v1は、前置増幅器1により、定
められた範囲内で振幅が変化するように増幅され
た画信号v2を生成する。画信号v2は、階調を人為
的に直線移動させるレンジ増幅器2により画信号
v3に変換させる。画信号v3は人為的に階調を変換
させる階調変換器3により画信号v4に変換され
る。操作卓4においては、人為的な階調変換を行
なうための制御信号を発生する機能を有し、レン
ジ増幅器2に対しては白レベル信号c1と黒レベル
信号c2を与え、第2図のような入出力特性で画信
号変換を施す。階調変換器3においては、入力画
信号v3を適当な関数Fを用いて、出力画信号v4に
対してv4=F(v3)なる変換を施す機能を有し関
数Fを階調補正曲線と呼びその一例を第3図に示
す。操作卓4からは階調変換器3に対してハイラ
イトレベルc3、ミドルトーンレベルc4およびシヤ
ドウレベルc5の各制御信号を与え、第3図のハイ
ライト領域5、ミドルトーン領域6およびシヤド
ウ領域7の各領域における直線8,9,10の傾
斜を制御する。このような直線の傾斜を制御する
方式としては、増幅器の負荷抵抗や帰還抵抗を可
変する方式がよく用いられている。第3図の階調
補正曲線は直線8,9,10から成る折線関数に
よつて関数Fが与えられていることを図示してい
るが、通常領域5,6,7の境界は予め定められ
た半固定的な値によつて区分されている。
上記のような従来例では、階調変換器3にいお
いてハイライト、ミドルトーン、シヤドウの3領
域に入力画信号v3のレベルを分割して信号変換処
理しているにすぎず、単純な階調補正曲線しか与
えることが出来ない。また人為的な階調補正曲線
を指示するに当つての原稿画像の濃度判断は人間
の視覚判断によつて行なわれるため、階調補正曲
線の関数Fを決める第3図の座標軸は濃度直線性
座標の方が人間工学的である。しかし第1図のよ
うな原稿画像の反射率比例な画信号の場合には、
第3図の座標軸は反射率直線性座標となり、原稿
画像の直感的判断での階調補正曲線の関数Fの設
定は困難で、通常こうした階調補正曲線の決定は
相当熟練を要する作業となつている。
発明の目的
本発明は、以上のような反射率比例な画信号に
対する階調変換処理における問題点を解決するた
めになされたもので、濃度座標軸を用いた階調補
正曲線を入力可能にするとともに、複雑な階調変
換も容易に処理可能な、信号処理方法を提供する
ことを目的とする。
発明の構成
この目的を達成するために本発明は、原稿画像
の反射光量に比例した画信号の振幅範囲を予め定
められたレベルに増幅してなる信号をデジタル変
換してデジタル入力画像信号を得、正規化入力濃
度対正規化出力濃度座標平面上に描いた階調補正
曲線上の複数の点の座標値ならびに白濃度と黒濃
度の値に基づいた階調変換曲線を示すデータを作
成しデジタル入力画信号を階調変換曲線を示すデ
ータによつて階調変換してデジタル出力画信号を
得る画信号処理装置に対して、階調変換曲線のデ
ータを作成する手順が、デジタル入力画信号をN
ビツト、最大デジタル出力画信号レベルをMと
し、入力される白濃度および黒濃度の値をそれぞ
れDW、DBとし、階調補正曲線上の複数の点Poの
座標値を(xo、yo)としたとき(N、nは自然
数)、デジタル入力画信号xiI対デジタル出力画信
号vpI座標平面上の点Po′の座標値(xo′、yo′)
を、
x1′=2N−1/1−10DW-DB{1−10(DW-DB)×xI}
y1′=M×y ただしI=1〜n
なる関係式より求め、前記デジタル入力画信号の
レベルviIを0から2−1まで順次更新しながら、
複数の点Po′の座表値xo′と比較して
xJ′viIxJ+1′(J=0〜n)なるJを求め、点
PJ′と点PJ′+1の間の直線を示す関数FJより、
vpI=FI(viI)
なる関数式より前記デジタル入力画信号viIに対す
る階調変換されたデジタル出力画信号vpIを得る
ものである。
実施例の説明
まず、本発明を実現する装置について図面を用
いて説明する。
第4図はその画信号処理装置の一実施例を示す
装置構成の概略図である。本実施例ではレンジ増
幅器2の出力画信号v3はA/D変換器11により
8ビツト並列なデジタル画信号v5に変換される。
画信号の階調を変換処理するモードにおいては、
アドレスセレクタ12によりデジタル画信号v5は
階調変換メモリ13のアドレス信号v6に直続さ
れ、予め設定された階調補正曲線から得られた画
信号変換値が記憶されている256バイトの領域か
ら成る階調変換メモリ13からのデータ読出しの
ためのアドレス信号として用いる、いわゆるメモ
リ参照方式によつて階調変換された8ビツト並列
なデジタル画信号v7を出力する。このようにデジ
タル画信号と参照メモリによる階調変換器を構成
することにより、後述するように複雑な補正曲線
に応じたデータ変換を容易に行なうことができ
る。
さて、従来例で指摘したように、反射率比例な
画信号処理経路に対しても濃度比例な座標系で階
調補正曲線を設定することが人間工学的である。
この場合、濃度比例な数値で階調補正曲線の関数
Fを設定可能にするために、座標変換演算をマイ
クロプロセツサを用いて行わせている。レンジ増
幅器2の出力画信号v3は、白濃度(DW)と黒濃
度(DB)が与えられたとき、原稿画像の濃度を
DXとすると
で表わされる。このような入力画信号に対しての
階調補正曲線の設定は、第5図のように、白濃度
(DW)を0、黒濃度(DB)を1とする。正規化入
力濃度座標軸(x軸)と、出力の白地濃度を0と
し黒地濃度を1とする正規化出力濃度座標軸(y
軸)の平面上で与えるのが最適である。正規化入
力座標軸上のxは、原稿画像濃度DXと、
x=(DX−DW)/(DB−DW)なる関係を有し、
したがつて入力画信号v3の画信号レベルに対応す
る第5図のx軸上のxcは第(1)式を用いて
xc=1/DB-DWlog〔1−v3{1−10-(DB-DW)}〕……(
2)
より求まる。
そして、この階調補正曲線は第5図のように複
数点P1〜Po(図ではPo=4まで)の折線関数で与
える。一方第4図の階調変換メモリ13への8ビ
ツト並列なデジタル画信号v5の0〜255の画信号
レベルに対応する8ビツト並列なデジタル画信号
v7の信号レベル値を階調補正曲線より求めるため
にマイクロプロセツサ14を用いている。第5図
の階調補正曲線上の複数点P1〜Poのx、y座標
値、(x1、y1)、(y2、y2)、……(xo、yo)は操作
卓15よりインターフエース16を介してマイク
ロプロセツサ14に入力し、マイクロプロセツサ
14内の記憶域17に順次記憶せしめる。またレ
ンジ増幅器2への白濃度(DW)、黒濃度(DB)の
値も操作卓15よりマイクロプロセツサ14内の
記憶域18に記憶せしめ、かつ
c1=10-DW
c2=10-DB ……(3)
なるデータ変換を施した後インタフエース19を
介してレンジ増幅器2に白レベル信号c1、黒レベ
ル信号c2を伝達する。
上記の階調補正曲線は正規化濃度座標系で与え
られているため、反射率比例なデジタル画信号v5
の0〜255の各レベルに対応する変換処理後のデ
ジタル画信号v7の画信号レベル値は、第5図の階
調補正曲線を第6図のように出力画信号レベル対
入力画信号レベルの座標軸平面上に変換した階調
変換曲線から求められねばならない。第6図の点
P1′〜P4′は、第5図中のP1〜P4に対応し、このよ
うな補正曲線を得る手順は、第6図のx軸上の任
意の座標点viよりv3=vi/255を求め、第(2)式より
正規化入力濃度値xcを得、第5図を用いて正規化
出力濃度ycを折線関数によつて表わされた階調補
正曲線より演算し、さらにvp=255×ycなる整数
化演算により求め第6図の座標軸平面に配置し階
調変換曲線を得る。
上記のような演算を施すために、第7図の処理
の流れ図に従つて行ないマイクロプロセツサ14
中の記憶域20に一時格納する。第8図は第7図
の処理の流れ図で用いる記憶域17,18,20
の各領域の配列例を示し、第8図aは記憶域17
の配列M1()を、bは記憶域18の配列M2
()を、cは記憶域20の配列M3()を例示
している。配列M1()は、第5図の入力座標点
P1〜Poの座標値の格納位置と点PIとPI+1間の直線
を表わすy=uo・x+Woなる式の勾配uoとy軸
切片WIの格納位置を例示し、nは入力された座
標点の箇数を示し、勾配uoと切片WIを求める手
順は、第7図の処理の流れ図中の手順1に示す。
第7図の手順1につづく手順2では、第4図の階
調変換メモリ13への入力画信号v5の0〜255の
信号レベルv1と第(2)式中の画信号レベルv3の関係
はv3=vi/255である事より、変位定数ΔK=1/
255を用いて入力画信号レベルv3の設定をした後
第5図中のx軸上の対応点xcの正規化入力濃度を
求め、同図中のいずれの直線領域で階調補正曲線
を近似するかを検索し、手順1で計算された直線
近似式の勾配と切片の値を選択し、正規化出力濃
度ycを得、さらに0〜255の範囲の整数化演算の
後第4図の記憶域20に第8図cの配列M3()
のように階調変換データとして記憶させる。
上記のような手順1、手順2で得られた階調変
換データは第4図のマイクロプロセツサ14よ
り、インタフエース21を介して階調変換メモリ
13へ順次書き込む。第4図の制御信号c6(以下、
制御信号、出力信号等のタイミング図を第9図に
示して説明する)は階調変換メモリ13の読出
し、書込みモード切替信号で、書込みモード時に
はアドレスセレクタ12をインタフエース21か
らの計数パルスc7を計数し0から255の値のアド
レス信号c8を発生するアドレスカウンタ22の出
力信号c8を階調変換メモリ13のアドレス線に接
続し、さらにA/D変換器11のサンプリング用
タイミング発生器23を休止状態に保持させる。
アドレスカウンタ22は、モード切替信号c6が書
込みモードに変化後の最初の計数パルスc7で計数
値を0にし、マイクロプロセツサ14の記憶域2
0から第8図cの配列M3()の順序に従い階調
変換データvpIを1データずつインタフエース2
1を介してデータ線c9に送出し、引続き信号線
c10に階調変換メモリ13への書込みクロツクを
送出する第7図に示した手順3を繰り返す。
第7図に示す処理の流れを第1表のような演算
速度を有するマイクロプロセツサで処理した場
合、手順1は0.05秒、手順2は5.05秒の時間を必
要とする。手順3は256バイトの単なるデータ転
送であるため処理時間への影響は極めて少い。第
1表から明白なように、手順1、手順2で最も時
間を要する演算は、指数、対数演算で、特に手順
2では256回の対数演算を要する流れとなつてい
る。
しかし、最近のような高速画像走査装置等にあ
つては上記のような階調補正曲線の演算処理のた
めの持ち時間は軽視できず更に高速な処理が望ま
れる。
INDUSTRIAL APPLICATION FIELD The present invention relates to an image signal processing method for performing gradation correction of an image signal obtained by reading a gradation image such as a photograph by photoelectric scanning. Conventional configuration and its problems In a device that processes a read image signal obtained by photoelectrically scanning a gradation original such as a photograph, such as an image scanner device or an imaging device, the read image signal is transferred to an image reading element or an image sensor. Various image signal processing circuits are provided for the purpose of matching the characteristics of recording or display elements and for the purpose of artificially processing the quality of images. In particular, many of recent image processing apparatuses have a function of artificially converting gradation characteristics. FIG. 1 shows processing of read image signal processing in a conventional image signal processing device.
In particular, the flow of processing related to gradation conversion is shown. In the conventional example shown in FIG. 1, the read image signal v 1 , which is inversely proportional to the index of the image density of the original, is an image signal amplified by the preamplifier 1 so that the amplitude varies within a predetermined range. Generate v 2 . The image signal v 2 is converted into an image signal by a range amplifier 2 that artificially moves the gradation in a straight line.
Convert it to v3 . The image signal v 3 is converted into an image signal v 4 by a gradation converter 3 that artificially converts the gradation. The console 4 has a function of generating control signals for performing artificial gradation conversion, and provides a white level signal c1 and a black level signal c2 to the range amplifier 2, as shown in FIG. Image signal conversion is performed using the input/output characteristics as follows. The gradation converter 3 has a function of converting the input image signal v 3 using an appropriate function F and converting the output image signal v 4 so that v 4 =F(v 3 ). This is called a key correction curve, and an example thereof is shown in FIG. Control signals for highlight level c 3 , middle tone level c 4 and shadow level c 5 are applied to the gradation converter 3 from the console 4 to control the highlight area 5, middle tone area 6 and shadow in FIG. The slopes of straight lines 8, 9, and 10 in each region of region 7 are controlled. As a method of controlling the slope of such a straight line, a method of varying the load resistance or feedback resistance of an amplifier is often used. The gradation correction curve in FIG. 3 shows that the function F is given by a broken line function consisting of straight lines 8, 9, and 10, but the boundaries of the normal areas 5, 6, and 7 are predetermined. The classification is based on semi-fixed values. In the conventional example described above, the gradation converter 3 simply divides the level of the input image signal v3 into three areas of highlight, middle tone, and shadow and performs signal conversion processing. It is only possible to give a gradation correction curve that is accurate. Furthermore, since the density of the original image is determined by human visual judgment when specifying the artificial gradation correction curve, the coordinate axes in Figure 3 that determine the function F of the gradation correction curve are based on density linearity. Coordinates are more ergonomic. However, in the case of an image signal proportional to the reflectance of the original image as shown in Figure 1,
The coordinate axes in Figure 3 are reflection straightness coordinates, and it is difficult to set the function F of the tone correction curve by intuitive judgment of the original image, and normally determining such a tone correction curve is a task that requires considerable skill. There is. Purpose of the Invention The present invention has been made in order to solve the above-mentioned problems in tone conversion processing for image signals proportional to reflectance. The present invention aims to provide a signal processing method that can easily process even complex gradation transformations. Structure of the Invention In order to achieve this object, the present invention obtains a digital input image signal by digitally converting a signal obtained by amplifying the amplitude range of an image signal proportional to the amount of reflected light of an original image to a predetermined level. , create data indicating a gradation conversion curve based on the coordinate values of multiple points on the gradation correction curve drawn on the normalized input density vs. normalized output density coordinate plane and the values of white density and black density, and digitally For an image signal processing device that converts the gradation of an input image signal using data representing a gradation conversion curve to obtain a digital output image signal, the procedure for creating the data of the gradation conversion curve involves converting the digital input image signal into a digital output image signal. N
The maximum digital output image signal level is M, the input white density and black density values are D W and D B , respectively, and the coordinate values of multiple points P o on the gradation correction curve are (x o , y o ) (N, n are natural numbers), the digital input image signal x iI vs. digital output image signal v pI The coordinate value of point P o ′ on the coordinate plane (x o ′, y o ′)
is obtained from the relational expression x 1 ′=2 N −1/1−10 DW-DB {1−10 ( DW-DB )×xI} y 1 ′=M While sequentially updating the level v iI of the input image signal from 0 to 2-1,
Compare the coordinate value x o ′ of multiple points P o ′ to find J such that x J ′v iI x J+1 ′ (J=0 to n), and
From the function F J that indicates a straight line between P J ′ and point P J ′ +1 , the tone-converted digital output image for the digital input image signal v iI is calculated from the functional formula v pI = F I (v iI ). This is to obtain the signal v pI . DESCRIPTION OF EMBODIMENTS First, an apparatus for realizing the present invention will be described with reference to the drawings. FIG. 4 is a schematic diagram of the device configuration showing one embodiment of the image signal processing device. In this embodiment, the output picture signal v3 of the range amplifier 2 is converted by the A/D converter 11 into an 8-bit parallel digital picture signal v5 .
In the mode that converts the gradation of the image signal,
The digital image signal v 5 is directly connected to the address signal v 6 of the gradation conversion memory 13 by the address selector 12, and is a 256-byte area in which image signal conversion values obtained from a preset gradation correction curve are stored. An 8-bit parallel digital image signal v7 whose gradation is converted by a so-called memory reference method is output, which is used as an address signal for reading data from the gradation conversion memory 13 consisting of the following. By configuring a tone converter using a digital image signal and a reference memory in this way, it is possible to easily perform data conversion according to a complicated correction curve as described later. Now, as pointed out in the conventional example, it is ergonomic to set the gradation correction curve in a coordinate system proportional to density even for an image signal processing path proportional to reflectance.
In this case, in order to make it possible to set the function F of the gradation correction curve with a value proportional to the density, a microprocessor is used to perform the coordinate transformation calculation. The output image signal v3 of the range amplifier 2 calculates the density of the original image when the white density (D W ) and black density (D B ) are given.
If D X It is expressed as The tone correction curve for such an input image signal is set by setting the white density (D W ) to 0 and the black density (D B ) to 1, as shown in FIG. The normalized input density coordinate axis (x axis) and the normalized output density coordinate axis (y
It is best to give it on the plane of the axis). x on the normalized input coordinate axis has the following relationship with the original image density DX : x = ( DX − D W )/( DB − D W ),
Therefore, x c on the x-axis in FIG. 5, which corresponds to the image signal level of the input image signal v 3 , can be calculated using equation (1) as x c = 1/D B-DW log [1-v 3 { 1-10 -(DB-DW )}〕……(
2) Determined by more. As shown in FIG. 5, this gradation correction curve is given by a broken line function of a plurality of points P 1 to P o (up to P o =4 in the figure). On the other hand, the 8-bit parallel digital image signal corresponding to the image signal level of 0 to 255 of the 8-bit parallel digital image signal v5 is sent to the gradation conversion memory 13 in FIG.
The microprocessor 14 is used to obtain the signal level value of v7 from the gradation correction curve. The x and y coordinate values of multiple points P 1 to P o on the gradation correction curve in Fig. 5, (x 1 , y 1 ), (y 2 , y 2 ), ... (x o , y o ) are The data is inputted from the console 15 to the microprocessor 14 via the interface 16 and stored in the storage area 17 within the microprocessor 14 in sequence. In addition, the values of white density (D W ) and black density (D B ) sent to the range amplifier 2 are also stored from the console 15 in the storage area 18 in the microprocessor 14, and c 1 = 10 - DW c 2 = 10. -DB (3) After performing data conversion, the white level signal c 1 and black level signal c 2 are transmitted to the range amplifier 2 via the interface 19. Since the above gradation correction curve is given in the normalized density coordinate system, the digital image signal v 5 is proportional to the reflectance.
The image signal level value of the digital image signal V7 after conversion processing corresponding to each level of 0 to 255 is calculated by converting the gradation correction curve in Figure 5 to the output image signal level versus input image signal level as shown in Figure 6. It must be determined from the gradation transformation curve transformed onto the coordinate axis plane. Points in Figure 6
P 1 ′ to P 4 ′ correspond to P 1 to P 4 in FIG. 5, and the procedure for obtaining such a correction curve is to calculate v 3 from any coordinate point v i on the = v i /255, obtain the normalized input density value x c from equation (2), and use Fig. 5 to calculate the normalized output density y c as a gradation correction curve expressed by a broken line function. Then, by calculating v p =255×y c to an integer, the obtained value is placed on the coordinate axis plane of FIG. 6, and a gradation conversion curve is obtained. In order to perform the above calculations, the microprocessor 14 executes the operations according to the processing flowchart shown in FIG.
It is temporarily stored in the storage area 20 inside. Figure 8 shows the storage areas 17, 18, 20 used in the flowchart of the process in Figure 7.
FIG. 8a shows an example of the arrangement of each area in the storage area 17.
array M 1 (), b is array M 2 of storage area 18
() and c exemplifies the array M 3 () of the storage area 20. Array M 1 () is the input coordinate point in Figure 5.
Examples of storage locations of coordinate values of P 1 to P o and storage locations of slope u o and y-axis intercept W I of the equation y=u o x + W o representing the straight line between points P I and P I+ 1 , n indicates the number of input coordinate points, and the procedure for determining the slope u o and the intercept W I is shown in step 1 in the processing flow chart of FIG.
In step 2 following step 1 in FIG. 7, the signal level v 1 of 0 to 255 of the input image signal v 5 to the gradation conversion memory 13 in FIG. 4 and the image signal level v 3 in equation (2) are Since the relationship is v 3 = v i /255, the displacement constant ΔK = 1/
After setting the input image signal level v3 using 255, find the normalized input density of the corresponding point xc on the x axis in Figure 5, and calculate the gradation correction curve in any straight line area in the figure. Search for the approximation, select the slope and intercept values of the linear approximation equation calculated in step 1, obtain the normalized output concentration y c , and after converting it into an integer in the range of 0 to 255, the result is shown in Figure 4. In the storage area 20 of FIG. 8c, the array M 3 ()
It is stored as gradation conversion data like this. The gradation conversion data obtained in steps 1 and 2 as described above are sequentially written into the gradation conversion memory 13 via the interface 21 from the microprocessor 14 shown in FIG. The control signal c 6 in Fig. 4 (hereinafter,
The timing chart of control signals, output signals, etc. is shown in FIG. 9 and will be explained) is a read/write mode switching signal for the gradation conversion memory 13. In the write mode, the address selector 12 is connected to the counting pulse c 7 from the interface 21. The output signal c8 of the address counter 22, which counts 0 to 255 and generates an address signal c8 with a value of 0 to 255, is connected to the address line of the gradation conversion memory 13, and further connected to the sampling timing generator of the A/D converter 11. 23 is held in a dormant state.
The address counter 22 sets the count value to 0 at the first count pulse c7 after the mode switching signal c6 changes to the write mode, and the address counter 22 sets the count value to 0 in the memory area 2 of the microprocessor 14.
The gradation conversion data v pI is sent one data at a time to the interface 2 according to the order of the array M 3 () from 0 to c in Figure 8.
1 to the data line c 9 , followed by the signal line
Step 3 shown in FIG. 7, in which the write clock to the gradation conversion memory 13 is sent out at step c10 , is repeated. When the processing flow shown in FIG. 7 is processed by a microprocessor having the calculation speed shown in Table 1, Step 1 requires 0.05 seconds and Step 2 requires 5.05 seconds. Since step 3 is simply a 256-byte data transfer, the impact on processing time is extremely small. As is clear from Table 1, the operations that require the most time in Steps 1 and 2 are exponent and logarithm operations, with Step 2 in particular requiring 256 logarithm operations. However, in the case of recent high-speed image scanning devices, etc., the time required for the calculation processing of the gradation correction curve as described above cannot be ignored, and even faster processing is desired.
【表】
こうした目的を達成するための、本発明では、
第5図の入力指示された階調補正曲線から第6図
の階調変換曲線を得るに当つて、第7図の処理方
式と異なる、第10図に示す処理方式とした。こ
の処理方式の原理は、第5図の階調補正曲線を規
定する複数点P1〜Poの座標のみを第6図の出力
画信号レベル対入力画信号レベル座標平面上に
P1′〜Po′点として配置し、点PI′とPI+1′間を直線
近似した直線群から成る折線関数を階調変換曲線
として用いようとするもので、第6図中の一点鎖
線がこれを表わしている。この処理方式では第6
図の点P1′〜P2′のように第7図の処理方式と比し
若干の誤差が発生する。しかし通常取扱う反射原
稿の画像濃度は黒濃度(DB)が2.0程度で相隣る
入力点のx座標の示す濃度差(xI+1−xI)+(DB−
DW)<2.0/5以下であれば、上記の誤差は階調
変換に殆んど影響を与えることはない。
第10図の処理方式では、第4図のマイクロプ
ロセツサ14内の装備した記憶域17に係る配列
を第11図の配列M1()のようにし、手順1′
において、
x′=255/1−10(DB-DW){1−10-(DB-DW).xI}……(4
)
の関係式よりxo′を求め配列M1(I)の所定位置に記
憶させ、
uI′=255(yI+1−yI)/xI+1′−xI′ ……(5)
の関係式よりuo′を求め配列M1′(I)の所定位置に
記憶させ、
wI′=255yI−uI′×xI′ ……(6)
の関係式よりwo′を求め配列M1(I)の所定位置に
記憶させる。
第10図の手順2′においては、第6図の入力
画信号レベルviの0〜255の値に対応して、いず
れの直線領域内にあるかを検索し、近似直線式の
勾配uJ′と切片wJ′を決定し
vpI=uJ′+ui+wJ′ ……(7)
の関係式により、出力画信号レベルvpIを求め第
8図の配列M3(I)のvpIに順次記憶させる。257個
の出力画信号レベルの演算後は第7図の手順3と
全く同様な手順で、第4図中のマイクロプロセツ
サ14内の記憶域20から256バイトの階調変換
データを階調変換メモリ13へ転送する。このよ
うな第2の処理方式を用いることにより階調補正
曲線の入力点数nを20として1.2秒に短縮される。
さらに第4図の構成を有する場合にはマイクロ
プロセツサ14内の記憶域17を磁気記録装置の
ような不揮発性の記憶域構成とすることにより、
第5図のような階調補正曲線を複数個用意してお
き、各曲線上の点P1〜Poの座標値の複数組のす
べてを一度操作卓15よりマイクロプロセツサ1
4に入力すれば長期に保存出来、それぞれの階調
補正曲線に対する番号等の曲線照合のための符号
を操作卓15より入力せしめ、既に保存されてい
る一組のP1〜Poの座標値を用いて第6図の階調
変換曲線を生成する手順を予めマイクロプロセツ
サ14に装着せしめておくことも容易に可能とな
る。かかる構成の場合には、階調変換に係る操作
は、各入力原稿画像に係る白濃度(DW)と黒濃
度(DB)および階調補正曲線の照合選択記号を
入力するだけでよく操作が著しく簡便になる。
発明の効果
以上のような本発明を用いることにより、従来
作業者の直感や経験に依存し、かつ極めて粗い階
調補正曲線の指示を、正規化出力濃度対正規化入
力濃度座標軸平面に描いた任意の階調補正曲線上
の複数点の座標値を指示することにより、人間の
視覚特性に合致した画像の濃淡変換指示を可能に
する許りでなく、種々の階調補正曲線を示す座標
値を入力しておくだけで、入力画像の濃度抽出処
理や階段状濃度分割処理等を含めた極めて広汎な
階調変換処理を容易に達成することが可能となつ
た。たとえば、昨今のコンピユータグラフイツク
等に見られるように人為的な画像を高速に形成す
る際に特に効果を有する。[Table] In order to achieve these objectives, the present invention:
In obtaining the gradation conversion curve of FIG. 6 from the inputted gradation correction curve of FIG. 5, the processing method shown in FIG. 10, which is different from the processing method of FIG. 7, was used. The principle of this processing method is that only the coordinates of multiple points P 1 to P o that define the gradation correction curve in Figure 5 are placed on the output image signal level vs. input image signal level coordinate plane in Figure 6.
The purpose is to use a broken line function consisting of a group of straight lines arranged as points P 1 ′ to P o ′ and a straight line approximation between points P I ′ and P I+1 ′ as a gradation conversion curve. This is indicated by the dashed dotted line. In this processing method, the sixth
Compared to the processing method shown in FIG. 7, some errors occur, such as points P 1 ' to P 2 ' in the figure. However, the image density of reflective originals that are usually handled has a black density (D B ) of about 2.0, and the density difference indicated by the x coordinates of adjacent input points (x I +1 − x I ) + (D B −
D W )<2.0/5 or less, the above error has almost no effect on tone conversion. In the processing method shown in FIG. 10, the array related to the storage area 17 installed in the microprocessor 14 shown in FIG. 4 is set as the array M 1 () shown in FIG.
In, x′=255/1−10 (DB-DW) {1−10 -(DB-DW).xI }……(4
) Find x o ′ from the relational expression and store it in a predetermined position of the array M 1 (I), u I ′=255(y I+1 −y I )/x I+1 ′−x I ′ ……( Find u o ′ from the relational expression in 5) and store it in a predetermined position in the array M 1 ′(I), then w I ′=255y I −u I ′×x I ′ ...... From the relational expression in (6), w o ' is determined and stored at a predetermined position in the array M 1 (I). In step 2' in FIG. 10, the input image signal level v i in FIG . ′ and the intercept w J ′ are determined, and the output image signal level v pI is determined using the relational expression v pI = u J ′ + u i + w J ′ ...(7). Store pI sequentially. After calculating the 257 output image signal levels, the 256-byte gradation conversion data is gradation-converted from the storage area 20 in the microprocessor 14 in FIG. 4 in exactly the same manner as step 3 in FIG. Transfer to memory 13. By using such a second processing method, when the number of input points n of the gradation correction curve is 20, the time can be shortened to 1.2 seconds. Furthermore, in the case of having the configuration shown in FIG. 4, by making the storage area 17 in the microprocessor 14 a non-volatile storage area configuration such as a magnetic recording device,
A plurality of gradation correction curves as shown in FIG .
4, it can be stored for a long time, and a code for curve matching, such as a number for each gradation correction curve, can be input from the console 15, and a set of already saved coordinate values of P 1 to P o can be saved. It is also possible to easily equip the microprocessor 14 in advance with a procedure for generating the gradation conversion curve shown in FIG. 6 using . In the case of such a configuration, operations related to gradation conversion can be performed simply by inputting the white density (D W ) and black density (D B ) for each input original image and the matching selection symbol for the gradation correction curve. becomes significantly simpler. Effects of the Invention By using the present invention as described above, it is possible to draw an extremely rough gradation correction curve instruction on the normalized output density versus normalized input density coordinate axis plane, which conventionally relied on the operator's intuition and experience. By specifying the coordinate values of multiple points on an arbitrary tone correction curve, it is possible to specify the gray scale conversion of an image that matches human visual characteristics, but also by specifying the coordinate values indicating various tone correction curves. By simply inputting , it is now possible to easily perform extremely wide-ranging gradation conversion processing, including density extraction processing, stepped density division processing, etc. of the input image. For example, it is particularly effective when creating artificial images at high speed, as seen in recent computer graphics.
第1図は従来の画信号処理装置における階調変
換部のブロツク図、第2図はレンジ増幅器の入出
力画信号特性図、第3図は従来の階調変換器の入
出力画信号特性図、第4図は本発明の画信号処理
方法に用いられる装置における階調変換部のブロ
ツク図、第5図は同操作卓より入力すべき階調補
正曲線の一例を示す図、第6図は第5図の階調変
換曲線より得られる階調変換曲線を示す図、第7
図は第5図の階調補正曲線を第6図の階調変換曲
線に変換する第1の処理方法を示す流れ図、第8
図a〜cは第7図の流れ図における記憶域の配列
例を示す図、第9図は第4図に基づく階調変換デ
ータの転送のためのタイミング図、第10図は本
発明の画信号処理方法における階調補正曲線を階
調変換曲線に変換する処理方法を示す流れ図、第
11図は第10図の実施例における記憶域の配列
例を示す図である。
1……前置増幅器、2……レンジ増幅器、3…
…階調変換器、4……操作卓、11……A/D変
換器、12……アドレスセレクタ、13……階調
変換メモリ、14……マイクロプロセツサ、15
……操作卓、16,21……インターフエース、
17,18,20……記憶域、22……アドレス
カウンタ、23……タイミング発生器、v1……入
力画信号、c1……白濃度(DW)、c2……黒濃度
(DB)c3〜c5……階調補正曲線の制御信号、v5…
…デジタル画信号、v8……アドレスデータ線、c9
……階調変換データ線。
Fig. 1 is a block diagram of a gradation converter in a conventional image signal processing device, Fig. 2 is an input/output image signal characteristic diagram of a range amplifier, and Fig. 3 is an input/output image signal characteristic diagram of a conventional gradation converter. , FIG. 4 is a block diagram of the gradation conversion section in the apparatus used in the image signal processing method of the present invention, FIG. 5 is a diagram showing an example of the gradation correction curve to be input from the console, and FIG. Figure 7 shows a gradation conversion curve obtained from the gradation conversion curve in Figure 5.
Figure 8 is a flowchart showing the first processing method for converting the gradation correction curve in Figure 5 to the gradation conversion curve in Figure 6;
Figures a to c are diagrams showing examples of storage area arrangement in the flowchart of Figure 7, Figure 9 is a timing diagram for transferring gradation conversion data based on Figure 4, and Figure 10 is an image signal of the present invention. 11 is a flowchart showing a processing method for converting a gradation correction curve into a gradation conversion curve in the processing method. FIG. 11 is a diagram showing an example of the arrangement of storage areas in the embodiment of FIG. 10. 1...Preamplifier, 2...Range amplifier, 3...
...Grade converter, 4...Operation console, 11...A/D converter, 12...Address selector, 13...Grade conversion memory, 14...Microprocessor, 15
...Operation console, 16, 21...Interface,
17, 18, 20...Storage area, 22...Address counter, 23...Timing generator, v1 ...Input image signal, c1 ...White density (D W ), c2 ...Black density (D B ) c3 to c5 ... Control signal for gradation correction curve, v5 ...
...Digital image signal, v 8 ...Address data line, c 9
...Gradation conversion data line.
Claims (1)
画信号の振幅を定められた振幅範囲で増幅する増
幅手段と、前記増幅手段の出力をデジタル入力画
信号に変換するアナログ/デジタル変換手段と、
正規化入力濃度対正規化出力濃度の座標軸平面に
おける複数の点の座標値ならびに白濃度と黒濃度
を入力する入力手段と、前記入力手段に入力され
た前記座標値ならびに白濃度と黒濃度から階調補
正曲線を作成する階調補正曲線作成手段と、前記
階調補正曲線作成手段が作成した階調補正曲線か
ら出力画信号レベル対入力画信号レベルの座標軸
平面における階調変換曲線を作成する階調変換曲
線作成手段と、前記アナログ/デジタル変換手段
の出力であるデジタル入力画信号を前記階調変換
曲線作成手段の階調変換曲線に基づき階調変換す
る階調変換手段とを具備する画信号処理装置に対
して、 前記階調変換曲線作成手段における階調変換曲
線のデータを作成する手順が、デジタル入力画信
号をNビツト、最大デジタル出力画信号レベルを
Mとし、前記入力手段から入力される白濃度およ
び黒濃度の値をそれぞれDW、DBとし、階調補正
曲線上の複数の点Poの座標値を(xo、yo)とした
とき(N、nは自然数)、デジタル入力画信号viI
対デジタル出力画信号vpI座標平面上の点Po′の座
標軸(xo′、yo′)を x1′=2N−1/1−10DW-DB{1−10(DW-DB)×xI} y1′=M×y1 (但し、=1〜n) なる関係式より求め、前記デジタル入力画信号の
レベルvi1 を0から2N−1まで順次更新しながら、複数の点
Po′の座標値xo′と比較してxJ′viIxJ+1′(J=
0〜n)なるJを求め、点PJ′と点PJ+1′の間の直
線を示すFJより、 vpI=FJ(viI) なる関係式より前記デジタル入力画信号viIに対す
る階調変調されたデジタル出力画信号vpIを得る
ものである画信号処理方法。[Scope of Claims] 1. Amplifying means for amplifying the amplitude of an analog read image signal proportional to the amount of reflected light of a document image within a predetermined amplitude range, and an analog/digital device for converting the output of the amplifying means into a digital input image signal. a conversion means;
an input means for inputting the coordinate values of a plurality of points on the coordinate axis plane of the normalized input density versus the normalized output density, as well as white density and black density; gradation correction curve creation means for creating a gradation correction curve; and gradation for creating a gradation conversion curve in a coordinate axis plane of output image signal level versus input image signal level from the gradation correction curve created by the gradation correction curve creation means. An image signal comprising: a tone conversion curve creating means; and a tone converting means for converting the tone of a digital input image signal, which is an output of the analog/digital converting means, based on the tone conversion curve of the tone conversion curve creating means. For the processing device, the procedure for creating gradation conversion curve data in the gradation conversion curve creation means is such that the digital input image signal is N bits, the maximum digital output image signal level is M, and the data is input from the input means. When the values of white density and black density are respectively D W and D B , and the coordinate values of multiple points P o on the gradation correction curve are (x o , y o ) (N, n are natural numbers), Digital input image signal v iI
The coordinate axes (x o ′, y o ′) of point P o ′ on the digital output image signal v pI coordinate plane are x 1 ′=2 N −1/1−10 DW-DB {1−10( DW-DB )×xI} y 1 ′=M× y 1 (where = 1 to n ) point
Compared with the coordinate value x o ′ of P o ′, x J ′v iI x J+1 ′ (J=
0 to n), and from F J indicating the straight line between point P J ′ and point P J+1 ′, use the relational expression v pI = F J (v iI ) to obtain the digital input image signal v iI An image signal processing method that obtains a gradation-modulated digital output image signal v pI for.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP57231807A JPS59117860A (en) | 1982-12-24 | 1982-12-24 | Picture signal processor |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP57231807A JPS59117860A (en) | 1982-12-24 | 1982-12-24 | Picture signal processor |
Publications (2)
Publication Number | Publication Date |
---|---|
JPS59117860A JPS59117860A (en) | 1984-07-07 |
JPH0519354B2 true JPH0519354B2 (en) | 1993-03-16 |
Family
ID=16929319
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP57231807A Granted JPS59117860A (en) | 1982-12-24 | 1982-12-24 | Picture signal processor |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPS59117860A (en) |
Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS61125281A (en) * | 1984-11-21 | 1986-06-12 | Fuji Photo Film Co Ltd | Image processing method |
JPH0719130B2 (en) * | 1985-03-26 | 1995-03-06 | コニカ株式会社 | Image display device |
JPH0634499B2 (en) * | 1987-06-24 | 1994-05-02 | 株式会社ヤマトヤ商会 | Photo engraving method |
JP2585289B2 (en) * | 1987-09-07 | 1997-02-26 | 株式会社東芝 | Reader |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS539411A (en) * | 1976-07-14 | 1978-01-27 | Nec Corp | Harmony correction circuit |
-
1982
- 1982-12-24 JP JP57231807A patent/JPS59117860A/en active Granted
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS539411A (en) * | 1976-07-14 | 1978-01-27 | Nec Corp | Harmony correction circuit |
Also Published As
Publication number | Publication date |
---|---|
JPS59117860A (en) | 1984-07-07 |
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